PNNL

Abstract

There is a need to develop reliable portable analytical systems for on-site and real-time biomonitoring of lead (Pb) from both occupational and environmental exposures. Saliva is an appealing matrix since it is easily obtainable, and therefore a potential substitute for blood since there is a reasonably good correlation between Pb levels in both blood and saliva. The microanalytical system is based on stripping voltammetry of Pb at the microelectrochemical cell having a flow injection/flow-onto design. Samples that contain as little as 1% saliva can cause electrode fouling, resulting in significantly reduced responsiveness, irreproducible quantitations, and the need for frequent electrode regeneration. In addition, incomplete Pb release from salivary protein can also yield a lower Pb response than expected. This paper evaluates the extent of in vitro Pb-protein binding and the optimal pre-treatment for releasing Pb from the saliva samples. Even in 50% by volume of rat saliva, the electrode fouling was not observed, due to the appropriate sample pretreatment (with 1.0 M acid, followed by centrifugation at the RCF of 15200×g) and the constant flow of the sample and acidic carrier that prevented passivation by the protein. The system offered a linear response over a low Pb range (1-10 ppb), low detection limit (1 ppb), excellent reproducibility (5% RSD), and reliability. It also yielded the same Pb concentrations in unknown samples as did the ICP-MS. These encouraging results suggest that the microanalytical system represents an important analytical advancement for real-time non-invasive (i.e., saliva) biomonitoring of Pb.